This invention relates to the subject matter of Disclosure Document No. 214,012, filed Nov. 9, 1988, which is incorporated herein by reference.
1. Field of the Invention
This invention relates to an improved multi-function brake valve for use in fluid pressure braking systems primarily employed on heavy-duty highway vehicles. More specifically, it relates to a compact, integrated, multi-function valve advantageously employed in semi-trailer brake systems which copes with the operating and safety requirements of modern towed vehicles with less complexity and fewer components and the potential for enhanced reliability, reduced maintenance and overall lower cost.
2. Discussion of the Prior Art
Modern heavy-duty braking systems for towed vehicles, particularly those encountered in tractor-trailer truck combinations, include systems having pressurized fluid storage reservoirs and a plurality of valves for controlling the application of the pressurized fluid. Representative prior-art systems are disclosed, for example, in Carton et al U.S. Pat. No. 3,992,064, issued Nov. 16, 1979, entitled "Vehicle Brake System" (reissued on Feb. 5, 1980 as Re. 30,205) and Fannin U.S. Pat. No. 4,182,535, issued Jan. 8, 1980, entitled "Trailer Brake System".
These prior art systems feature dual reservoirs and related piping and valving systems which control communication of fluid pressure to the reservoirs and communication of the pressurized fluid from either of the reservoirs to the spring-actuated, fluid-pressure-released parking brakes. The systems are designed so that the integrity of the service and parking brakes are not totally compromised by limited system failures, as described in considerable detail in these typical prior art references and as more fully set forth hereinafter. To achieve such objective, the prior art systems rely upon a multiplicity of non-integrated components including a plurality of separate check valves or equivalent which are characterized by complexity, substantial space requirements, higher component costs, greater installation maintenance charges and attendant problems.
The improved multi-function valve of the present invention lends itself to the same types of braking systems as employed in the prior art and accomplishes substantially the same functions with enhanced performance. As will be apparent from the description herein, the valve of the present invention also results in less complexity, fewer components and attendant space saving. This simplification provides the potential for enhanced reliability, reduced investment, and lower installation and maintenance costs.
In general, the functions which the improved valve of the present convention carries out include the following:
(a) It communicates the pressurized fluid from a source thereof to the dual reservoirs of the system. PA1 (b) It provides communication of fluid pressure from the source thereof and/or from the dual reservoirs for applying and releasing the parking brakes. PA1 (c) It protects each reservoir against loss of fluid pressure due to failure or leakage in the system between each reservoir and its source of fluid pressure. PA1 (d) It provides communication of fluid pressure from each reservoir independently of the other reservoir to the parking brake actuators so as to release the fluid-pressure-released parking brakes.
In accomplishing these functions using pressurized air as the fluid medium for such purposes, the multi-function valve of the present invention meets all the requirements of the pertinent portions of Federal Regulation FMVSS 121.